Core Configuration
Symphony DSP56724/DSP56725 Multi-Core Audio Processors, Rev. 0
Freescale Semiconductor
5-3
5.3
Status Register (SR)
The Status Register (SR) (
) is a 24-bit register that consists of three 8-bit control registers. These
three registers are defined within the SR primarily for compatibility with other Freescale DSPs.
•
Extended Mode Register (EMR) (SR[23:16]):
Defines the current system state of the processor. The EMR bits are affected by hardware reset,
exception processing, DO FOREVER instructions, ENDDO (end current DO loop) instructions,
BRKcc instructions, RTI (return from interrupt) instructions, TRAP instructions, and instructions
that specify the Status Register (SR) as their destination (for example, MOVEC). During hardware
reset, all EMR bits are cleared.
•
Mode Register (MR) (SR[15:8]):
Defines the current system state of the processor. The MR bits are affected by hardware reset,
exception processing, DO instructions, ENDDO (end current DO loop) instructions, RTI (return
from interrupt) instructions, TRAP instructions, and instructions that directly reference the Mode
Register (MR) (for example, ANDI, ORI, or instructions, such as MOVEC, that specify the Status
Register (SR) as the destination). During hardware reset, the interrupt mask bits are set and all other
bits are cleared.
•
Condition Code Register (CCR) (SR[7:0]):
Defines the results of previous arithmetic computations. The CCR register bits are affected by Data
Arithmetic Logic Unit (Data ALU) operations, parallel move operations, instructions that directly
reference the CCR register (ORI and ANDI), and by instructions that specify the Status Register
(SR) as a destination (for example, MOVEC). Parallel move operations affect only the S and L bits
of the CCR register. During hardware reset, all CCR register bits are cleared.
The Status Register is pushed onto the System Stack when the following conditions are true:
•
Program looping is initialized
•
A JSR is performed, including long interrupts
3
MD
*
Operating Mode D
See the
DSP56300 FM 5.4.1.1 Operation Mode Register(OMR)
2
MC
*
Operating Mode C
See the
DSP56300 FM 5.4.1.1 Operation Mode Register(OMR)
1
MB
*
Operating Mode B
See the
DSP56300 FM 5.4.1.1 Operation Mode Register(OMR)
0
MA
*
Operating Mode A
See the
DSP56300 FM 5.4.1.1 Operation Mode Register(OMR)
Table 5-2. Operation Mode Register Bit Definitions (Continued)
Bit
Number
Bit
Name
Reset
Value
Description